There has hitherto been known an image forming apparatus capable of duplex printing for forming images on both surfaces of a sheet.
It has been proposed that, in this type of image forming apparatus, a duplex (DX) outlet for switching back sheets should be provided separately from an outlet through which sheets are discharged onto a sheet discharge tray. In simplex printing for forming an image on one surface of a sheet, after an image is formed on one of the surfaces of a sheet in an image forming device, the sheet is discharged onto the sheet discharge tray through the outlet. In duplex printing, after an image is formed on one surface of a sheet in the image forming device, the sheet is sent out from the DX outlet toward the sheet discharge tray, and the conveying direction of the sheet is reversed (switched back) in a state in which a trailing edge of the sheet remains in the apparatus. The sheet, of which conveying direction is switched back, is conveyed through a reverse conveying path and is sent into the image forming device with front and back surfaces thereof inverted, and an image is formed on the other surface of the sheet in the image forming device. After the images are formed on both surfaces of the sheet, the sheet is discharged onto the sheet discharge tray through the outlet.
In such a structure, when the sheet is sent out from the DX outlet toward the sheet discharge tray, it sometimes contacts another sheet, for example, stacked on the sheet discharge tray or being discharged from the outlet. If the sheet discharged from the DX outlet contacts the other sheet, it is sometimes buckled, or the other sheet is sometimes electrostatically attracted to the sheet. This causes a jam and double feeding.